Friday, March 2, 2012

Volume of Rectangular and Triangular Prisms

How to Find the Volume of Rectangular and Triangular Prisms

Volume is the amount of 3-D space that a object takes up. Volume is measured in cubic units, because volume is 3-D and a cube is a 2-D square with another dimension. A rectangular prism is just what it sounds like, a prism made of rectangles. Think of a cube, but rectangular faces, so a little stretched out. A triangular prism is almost like a rectangular prism, but it’s end faces are triangles. If you look at the prisms below, you can see that there are three parts labelled h, b, and l or w. That h, b, and l or w stands for height, base and length or width (height, width and length being the first 3 dimensions, and the dimensions of a cube). So, volume is basically figuring out how many of those cubed units fit in a figure. If area is figuring out how many squared units are in a figure, and the formula for finding area for a rectangle is length by width, and a rectangular prism is a rectangle with height, it is logical for volume=height*length*width to be the formula for a rectangular prism. You may see this formula, but it is more likely that you will see v=hlw, the shortened version. The same theory goes for triangular prisms. If the formula for area is a= 1/2 lw, add height to make it v= 1/2 hlw. Below are so practice problems and videos, and a very short Voki.

The following video gives and excellent representation of how cubic units work to determine volume. Be sure to watch it to get a clear understanding.

This video explains triangular prisms and provides a couple of examples.